Siphopteron flavolineatum

Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Order: Cephalaspidea
Family: Gastropteridae
Genus: Siphopteron
Species: Siphopteron flavolineatum

Siphopteron flavolineatum is a tiny headshield slug in the family Gastropteridae. Headshield slugs are not nudibranchs, and gastropterids are known for their wing-like side flaps, which some species use to swim.

The animal in these photos is the colour form the book lists as variety 2. It is bright orange with a pointed tail, and only a few millimetres long.

Siphopteron species usually live on sand and rubble, where their colours make them stand out once you know what to look for.

In the Philippines they are a classic muck diving find. Move slowly over the sand with a focused light, and use a diopter or strong macro setup to get the detail.

It appears on page 312 of Nudibranchs of the Philippines.